This invention relates to a joint structure of a metallic pipe to a metallic container, and particularly relates to a joint structure of a breather pipe to a fuel tank for a vehicle or the like.
A metallic breather pipe for adjusting pressure in a metallic fuel tank and detecting fuel supply amount at fuel supply is mounted to the fuel tank for a vehicle or the like together with an inlet pipe for fuel supply. The breather pipe is jointed to the tank in such a fashion that a part thereof is inserted in the fuel tank. An end part of the pipe which is inserted in the fuel tank is opened at an upper limit of liquid level of fuel in the fuel tank. The other end part of the breather pipe is connected to a vicinity of a fuel injection mouth of the inlet pipe.
The metallic breather pipe is conventionally jointed to the metallic fuel tank in such a manner that: a flange is mounted at a middle part of the breather pipe; the flange is jointed to the tank by, for example, spot welding; then an entire periphery of the pipe at jointed part is sealed by using a solder for keeping a sealed condition between the breather pipe and the tank.
Japanese Patent Publication No. 63-36878 discloses a technique that: an expanded part (flange or flare) is formed at one end of a metallic pipe and a through hole is formed at a part of a metallic plate at which the metallic pipe is jointed; the metallic pipe is inserted through the through hole of the metallic plate; then the expanded part of the metallic pipe is jointed to the inner periphery of the through hole by projection welding. This reference relates to the joint of the end part of the metallic pipe to one side surface of the metallic plate, which means that there is no disclosure about the joint structure that the metallic pipe passes through and is joined at the middle part thereof to the metallic plate.
Also, well known is a joint structure of a pipe to a tank that in a fuel tank made of synthetic resin a tubular part opening into the fuel tank is formed and a pipe is inserted in the tubular part. This joint structure is, however, different from the joint technique in which the metallic pipe passes through the wall of the metallic fuel tank.
In the conventional technique that the joint part between the metallic breather pipe and the metallic fuel tank is entirely sealed by a solder, lead in the solder is melt out at a cleaning treatment after the process, which involves increased processing cost for preventing pollution of drain due to cleaning. In addition, soldering for sealing the entire periphery requires skilled persons, which means low productivity.
The inventors in the present invention have tried to ensure the sealability without soldering by welding the flange to the wall of the tank by projection welding after the flange is mounted at a middle part of the metallic breather pipe.
However, in this case, the projection welding can be conducted with an ordinary electrode of a projection welding device only when the electrode is divided.
The present invention has its object of ensuring the sealability and joint strength at joint part of the metallic pipe passing through the wall part of the metallic container with projection welding by using the ordinary electrode.